Mark M. Peyton and Jeremiah L. Maher, Central Nebraska Public Power and Irrigation District, Holdrege, Nebraska

INTRODUCTION

In response to concerns expressed over the effects of hydropower and irrigation on the presence of freshwater mussels in the Platte River, the Central Nebraska Public Power and Irrigation District (Central) initiated a survey in 1991 for freshwater mussels in the upper Platte River and associated irrigation and power canals and lakes within this stretch of river.

From 1991 through 1994, 19 sites consisting of 30 kilometers of river and 20 kilometers of canals were surveyed, as well as ten canal lakes. The results of those surveys are presented here.

BACKGROUND

There were three recent studies of freshwater mussels done prior to these surveys on the upper and central Platte River system. Roedel (1990) studied two sites located in the central Platte River near Wood River, Hall County, Nebraska; Lingle (1992) studied a 2.4-kilometer stretch of the central Platte that included the Roedel sites; and Perkins (Freeman and Perkins, 1992) surveyed the entire Platte including associated sloughs and ponds from Plattsmouth to the Wyoming border. Perkins' work incorporated the findings of Roedel, Lingle and the early work of Central. A list of ten species was developed for the Platte River from these studies (Table 1).

STUDY AREA

The area of the Platte River valley surveyed for this study extends approximately 120 kilometers west from Overton, Nebraska (Figure 1). A number of smaller irrigation canals have their diversions at points within this reach. The Phelps Canal has its origin at the terminus of Central's Supply Canal which diverts water near North Platte, Nebraska, and parallels the river for this entire stretch. A number of small and medium-sized lakes are formed by the Supply Canal.

METHODS

Nineteen sites consisting of approximately 30 kilometers of river and 20 kilometers of irrigation canals as well as ten canal lakes were surveyed visually and tactually while walking or swimming. A limited number of specimens were collected as vouchers to verify species identification. All other specimens were returned to their original location. Voucher specimens were submitted to the University of Nebraska State Museum Research Collection.

RESULTS

We located and identified 8,804 specimens representing nine native species of freshwater mussels (Table 2). Eighteen specimens, representing five native species, were found in 30 kilometers of the Platte River while 8,206 specimens, representing nine native species, were identified in 20 kilometers of irrigation canals. In addition, 580 specimens representing seven species were located within the ten lakes surveyed.

Four species not previously collected in the Platte River system, or whose existence had been questioned, were located in our surveys. The Asiatic clam (Corbicula fluminea), an exotic whose method of introduction into the Platte system is unknown, was located in a number of canals and in the river from the confluence of the North and South Platte rivers to Cozad, Dawson County, Nebraska. The liliput shell (Toxolasma parvus) was located in portions of Johnson Lake and the fingernail clam (Sphaerium sp) was found in a number of places as dead valves only. Live Sphaerium is present in the Sutherland canal west of the study area and it is believed that all finds in this study were those that had been carried down through the system.

The squawfoot (Strophitus undulatus) was first reported from the Platte by Roedel (1990). However, Perkins (Freeman and Perkins, 1992) questioned the find based on a review of the voucher specimens by Dr. David Stansbury of Ohio State University. Specimens collected in this study believed to be S. undulatus were sent to the University of Colorado for verification. Using valve characteristics and softbody dissection, Dr. Hsiu-Ping Liu and Dr. Shi-Kuei Wu verified the identification of these specimens as S. undulatus.

Three species made up 95.6% of all specimens identified (Table 2). The white heelsplitter (L. complanata) (79.6%) was the most numerous species in the smaller irrigation canals, Phelps Canal and the Supply Canal.

The pink paper shell (P. ohiensis), (11%) also called the pink heelsplitter, was the most abundant species of freshwater mussel found in the lakes and in the river channels.

The maple leaf (O. quadrula) was identified by Freeman and Perkins (1992) as the most abundant species of freshwater mussels in the Platte. However, no specimens of maple leaf clams were found in 30 kilometers of river channel during Central's study. The maple leaf accounted for 4.7% of all specimens collected and was the second most abundant species found in the lakes and was fairly common in the smaller irrigation canals.

DISCUSSION

Studies done by Roedel (1990), Freeman and Perkins (1992), Lingle (1992) and now this study, show limited use of the Platte River by freshwater mussels. Based upon the location and identification of more than 8,000 specimens of mussels from hydro and irrigation canals and their associated lakes it is clear that these bodies of water do provide habitat which supports large populations of freshwater mussels.

The common occurrence of mussels in the canal systems as opposed to the sparse collection records from the river channels may have a number of explanations. The shifting sand bottom and constantly changing configuration of channels, along with the extreme flow changes common on the river, may not be as conducive to the existence of mussel beds as is the gravel and mud bottoms and more stable flows found within the canal system.

Also of importance is the presence or absence of fish species that act as hosts for the parasitic larval stages of many species of mussels. The common host fish for the 11 species of freshwater mussels located in the Platte River (Table 3) account for less than 5% of the more than 81,000 fish collected between 1990 and 1993 in a study of the abundance and diversity of fish in the various habitats of the central Platte River (Chadwick, 1994).

SUMMARY

Several species of freshwater mussels live in the canal systems and their associated lakes, drains, and returns of the upper Platte valley. Most of these species prefer habitats of silty, slow moving or ponded water and require host species not historically found in abundance in the Platte River system. Man-made reservoirs and canals and the introduction of new fish species to the system may have contributed to the current distribution and abundance of freshwater mussels in this region of the Great Plains.

REFERENCES

Chadwick and Associates. 1994. Forage fish monitoring study central Platte River, Nebraska 1993. Unpublished report prepared for the Nebraska Public Power District and the Central Nebraska Public Power and Irrigation District: 55p.

Freeman, Patricia W. and Keith Perkins. 1992. Survey of mollusks of the Platte River. Unpublished report prepared for the U.S. Fish and Wildlife Service, Grand Island, Nebraska: 37p.

Lingle, Kari L. 1992. Habitat and microhabitat preferences of adult freshwater mussels (Mollusca: Bivalvaia: Unionidae) of the Platte River, Nebraska. Masters Thesis, University of Nebraska-Kearney: 237p.

Roedel, Michael D. 1990. Unionid mollusks in the big bend reach of the Platte river, Nebraska. Prairie Naturalist 22(1):27-32.

Return to 1995 Platte River Basin Ecosystem Symposium

Last updated by Darren A. Jack on 6/11/97